Study the Block Diagram
Tip 25: Obtain a copy of the Guth Laboratories, Inc. #duisimulator "Model 2100 Simulator Operation Manual" and study the "Model 2100-Block Diagram" at page 13. Notice the "Display Section-34.0C- Multiplexed Display Driver" and "RS-232 Level Converter".
These two temperature data systems are connected to the "8051 Micro Controller". Their source of temperature information appears to be the one micro controller. They do not appear to have sources of temperature information independent of each other. They receive their temperature information from the same source and so it is always the same information, except that one display may have two decimal places (the RS232 interface to the 8000C) and the other may have one decimal place (the Guth 2100 display).
But most importantly, neither display appears to have a source of temperature information (a probe independently sensing temperature), separate from the "precision thermistor", the thermostat that (through the micro controller) controls the Guth 2100 heater. NEITHER THE DIGITAL DISPLAY THERMOMETER NOR THE RS232 THERMOMETER APPEAR TO BE INDEPENDENT OF THE HEATER CONTROLLED BY THE "PRECISION THERMISTOR".
It therefore appears that the only reliable method for a QT to check the solution temperature is to manually observe the temperature indicated on the (OPTIONAL) yellow NIST mercury thermometer. It appears that police services who rely entirely on the Guth 2100 digital display or the RS232 interface are not independently checking the simulator temperature. All they are doing, if they rely on the digital display or the RS232 system, is relying on a reading of the thermistor temperature controlling the heater.
If you have information from the manufacturer that contradicts this inference please phone the author immediately at 1-877-273-3322 and this blog entry will be corrected accordingly.
Perhaps it is, because the digital display/RS232 display system is not independent of the heater thermistor, that Qualified Technicians are trained, since 2010, "It is recommended that a NIST mercury thermometer is used when using a digital simulator to confirm the display temperature." See Tip 6 Verification of Digital Thermometer herein.